11.6.7 Grading-up

This is the method used to change a population of animals quickly from one breed to another. Sires of the newly desired breed are continually backcrossed to the females from the previous generation. After three generations the F₃ animals contain already for 87,5 % the genes of the desired breed and after four or five generations the population fully resembles the desired parental breed. Such a process took place in Western Europe in the 70-ties of the past century when local Black and White cattle populations were graded-up with Holstein Friesian sires from North America creating the present European Holstein Friesian cattle breed.

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Percentage of Dutch Friesian and Holstein Friesian genes in Dutch Black and White cows per year of birth. (Source: CRV)

The figure above shows the rapid replacement by upgrading of the Dutch Friesian by the Holstein Friesians from North America. The downside of grading-up is that original breed may disappear. For instance, the Dutch Friesian is a small population nowadays